1. Field
The present disclosure relates generally to glass reforming. More particularly, the present disclosure relates to heating of a mold and glass sheet to target mold and glass forming temperatures, respectively, using a common heat source.
2. Description of the Related Art
Glass sheet reforming process involves placing a glass sheet on a mold, heating the glass sheet and mold to their respective forming temperatures, and forming the glass sheet into a shaped glass article. Forming of the glass sheet involves conforming the glass sheet to a shaping surface of the mold. The mold is typically made of metal and has to be operated at temperatures that would avoid failure of the mold material and/or rapid decline of the shaping surface quality. Often, this means that the glass has a maximum permissible temperature when in contact with the shaping surface. However, the glass temperature cannot be too low to the point that it is impossible to form the glass without damaging the glass. The result is that each of the mold and glass sheet will have relatively narrowly defined temperature targets that must be attained at the time that the forming of the glass sheet starts in order to have a successful forming of the glass.
Typically, both the glass sheet and mold begin at temperatures below their desired forming temperatures and are heated together in a common furnace or series of furnaces until their respective forming temperatures are achieved. In some furnace systems, the mold will reach its target forming temperature sooner than the glass sheet, requiring extra mold cooling to slow down the heating rate of the mold and allow more time for the glass sheet to heat up to its target forming temperature. In other furnace configurations, the glass sheet will heat up too quickly, requiring that the furnace temperature must be reduced to maintain the glass temperature effectively in an equilibrium state between the slowly heating mold and the furnace walls until both the mold and glass sheet reach their respective targets. Both of these methods yield a slower process than necessary and are difficult to control precisely.